Preheat oven to 400F degrees. Cover a large sheet pan with foil or parchment, lightly spray olive oil and set aside.
Meanwhile, combine sesame oil, garlic, ginger, soy sauce, vinegar and brown sugar in a small bowl and mix. Pour into a large ziplock bag and add salmon, marinate 10 minutes.
In a medium bowl, toss broccoli and peppers with 1 tablespoon sesame oil, ¼ teaspoon salt and pepper. Spread them evenly on prepared sheet pan and roast for 10 minutes.
Remove veggies from oven, toss, and move them over slightly to make room for the salmon. Place the salmon on the sheet pan, reserving the marinade and return to oven, roast an additional 7 to 8 minutes, or until salmon is just cooked through.
While salmon is cooking, heat a small skillet over low heat. Pour the remaining marinade and simmer stirring until the sauce has thickened slightly, about 1 to 1 1/2 minutes.
Brush sauce over salmon and sprinkle fillets with sesame seeds and scallions. Serve with veggies on the side.